<p>I just got a new Macbook Pro last week, and I've kept it charged from the day I got it until now. I know some people say it's best to keep it unplugged and discharge/recharge it every time, but a friend of mine who is a long-time Mac user said its okay to keep it plugged. But about 2 days after my first use of the new MBP, the charge on the laptop went down from 100% to 98%, even though I've never unplugged from the charger. Now today when I turned it on, it went down to 97% charge. Why does the battery charge keep going down if I'm leaving it plugged the whole time? Shouldn't it stay at 100% charge if its never unplugged from the charger?</p>
<p>Just a chemistry note: the lithium ion batteries that all modern laptops (and electronics, for that matter) use do degrade if they are left at full charge. You should unplug your computer if you’re not using it for extended periods of time, and run the battery down once in a while.</p>
<p>As for your percentage issue, that is likely a glitch with the battery monitoring. It might read the voltage of the battery and compare it to what the voltage should be at various charge states. If the voltage is slightly low for whatever reason (which may or may not indicate a problem with your battery) then it might interpret that as battery at not-full charge.</p>
<p>It could be a faulty battery. Tons of laptops have faulty batteries, not just PC’s. As a personal story, my old laptop’s battery and AC adapter died after 2 years.</p>
<p>Or pay a visit to the Apple store. They’re filled with geeks (in a good way).</p>
<p>Hawkwings hit the nail on the head, Lithium Ion battery’s must be run dead every once in awhile or they start to deteriorate, I bet if you read through the documentation somewhere it will say this. I know Apple recommends one full run down and charge up per month of the lithium ion battery in its iphone and ipod touch. </p>
<p>Here is one better, straight from apple. </p>
<p>[Apple</a> - Batteries - Notebooks](<a href=“http://www.apple.com/batteries/notebooks.html]Apple”>Batteries - Maximizing Performance - Apple)</p>
<p>Yeah I’ve already seen that recommendation by Apple, and I plan on doing that once every month. The thing is, it hasn’t even been more than a week, let alone a month, since I got my macbook. Yet the battery is down to 97% even with the charger plugged in 24/7.</p>